Quote by traianus
Thank you for your answer. The function I have is delta (tu), which is similar (in concept) to the function delta(t). The function delta(t) is infinite when t = 0. So I deduce that delta (tu) is infinite when tu=0. Right? If so something does not work. Please convince me!

t is never zero in delta(tt+) the t+ means we always chose a number larger than t. Thus we always get zero. It is like delta(0+) we chose a number larger than zero (but in a limit process ever closer to zero) thus we always get zero.
delta(0+)=0
delta(tt+)=0
this is much like the nonsingular case define
f(x)=0 x!=0(x not zero)
f(x)=1 x=0
f(0+)=0
Limits care about the journey not the destination. The whole point of using limits is to find out what happen as we approch a value when we do not like or do not care about what happens at the value.